A vibrant Northern Blacktailed Rattlesnake hiding away in a crevice in Pinal County, Arizona. These rattlesnakes are one of the species most often encountered by hikers, but are comparatively rarely found at homes. They’re secretive snakes, and easy to walk right by in most instances.
These sideblotched lizards are common and found about everywhere. Even in urban Phoenix and Tucson, they can be seen running around on the maze of block walls and stucco. This one is particularly colorful, found in northern Arizona.
If you walk a stream in much of Arizona right now, there’s a good chance you’ll run into one of these. It’s a Black-necked Gartersnake, getting breath and a break between dives to eat tadpoles. In any of the isolated pools along this drainage, there may be one or two, filling up on these seasonal globs of protein while they can. This particular snake is a very small baby, likely not much different in age than the tadpoles it’s hunting.
A Mojave Rattlesnake near Phoenix, Arizona last year. This relatively young snake. While the old idea of counting rattle segments to tell the age of a snake isn’t accurate, much can still be learned. For instance, this snake still has its prebutton intact, which it was born with – its first shed skin revealing the full button. Then two articulated segments, and a the basal segment mean this snake has shed three times in its life. Given the strong and steady taper of segments and very healthy weight, and time of year it was found (late in the monsoon): this snake had just had its first birthday. As usual, it’s not green … and not “aggressive”. These timid snakes, like any other rattlesnake … or any other animal … will do all they can to prevent their own death. Add in a lifetime of hearing from everyone around that they are aggressive and chase you down on sight, not a small amount of social media distortion, and a sprinkle of personal identity reliance on contrived threats, and you have the most feared animal in the West.
But if this is you … it’s not your fault. Your brain can lie to you. In fact, with things you may fear, it can do so quite effectively. So while many stories of Mojaves chasing someone through the desert are flat-out lies, many are not. The reason: just like the snake, you are programmed for survival. In some cases, this means adding a few exclamation points to perception and memory.
And if you don’t buy that your brain can lie to you: open a new tab and look up any optical illusion. Right there in front of you: your brain is lying. Then, read these publications:
1. Riskind, J. H., Moore, R., & Bowley, L. (1995).
The looming of spiders: The fearful perceptual distortion of movement and menace. Behaviour Research and Therapy, 33(2), 171–178. https://www.sciencedirect.com/science/article/pii/0005796794E0023C
This paper explores how fear increases the perceived motion and menace of feared objects such as spiders and snakes. Fearful individuals overestimated the movement of spiders/snakes, evidencing distorted space/time perception under phobic conditions.
2. Öhman, A., & Mineka, S. (2003).
The malicious serpent: Snakes as a prototypical stimulus for an evolved module of fear. Current Directions in Psychological Science, 12(1), 5–9. https://journals.sagepub.com/doi/abs/10.1111/1467-8721.01211
This article theorizes that fear of snakes activates an “evolved fear module” in the brain, causing rapid and automatic responses to snake stimuli. It suggests deep-rooted neurocognitive pathways shape the perception of danger.
3. Teachman, B. A., Gregg, A. P., & Woody, S. R. (2001).
Implicit associations for fear-relevant stimuli among individuals with snake and spider fears. Journal of Abnormal Psychology, 110(2), 226–235. https://www.academia.edu/download/49240316
Using implicit association tests, this paper reveals distorted cognitive processing of snake stimuli in phobic individuals. It supports the idea that fear biases long-term memory and perception of threat magnitude.
4. Soares, S. C. (2010).
Fear commands attention: Snakes as the archetypal fear stimulus? [Doctoral dissertation]. Karolinska Institutet. https://openarchive.ki.se/articles/thesis/Fear_commands_attention_snakes_as_the_archetypal_fear_stimulus_/26901778/1/files/48943789.pdf
This dissertation offers detailed experiments demonstrating that snakes command disproportionate attentional resources, even in peripheral vision, leading to spatial distortion and overestimated danger.
A young Fer De Lance in Peru. These snakes can appear anywhere and everywhere, so watching every step and hand fall is a must. I’m always happy to see one though.
An Arizona Ridgenosed Rattlesnake with her newborns.
Like many snakes, including all vipers in the U.S., these rattlesnakes do not lay eggs. They give live birth to young, which stay with the mother for a period of time afterward. Once they’ve shed skin for the first time, around ten days later, they will disperse. In the meantime, these little ones spend time with their moth, following her lead on their first experiences with a big, dangerous world.
A Blacktailed Rattlesnake hiding out just outside its den. It took a few years to zero in on the exact spot, surveying the area in early spring and late fall and tracking where snakes were found in early egress. Eventually, there it was – with just two snakes in it to start, but the start of many more to come. The snake wasn’t disturbed, and due to the location, very likely may have never seen a human before.
A Greater Short-horned Lizard from central Arizona.
No doubt the comments will be full of “we call em horny toads as kids”. But, there’s more to it 🙂 These are lizards, rather than toads … which is a surprise to many born-and-raised Arizona residents.
There are also SEVEN distinct species of them in our state, all with their own appearance, habitat preferences, and specialized diet. So the “horny toads” you may recall playing with as kids may be entirely different than the species discussed.
And a favorite example of how confirmation bias can shape our perception of the world: another comment we always get on these posts is “used to see them all the time as a kid, not so much anymore”. While the population is in decline for some species, this is easily answered by answering this question: do you spend less time outdoors playing in the dirt as an older adult?
A Sonoran Sidewinder from the Phoenix area, out and about late at night as they tend to do. This one is large, for a small species, and for a male. These snakes are under two feet long, with females being slightly larger as full-grown adults. There are several reasons this may be the case, one of which being that a bigger snake can produce more babies.
These rattlesnakes don’t, and may not really be able to, slither like most snakes do. They can move in a straight line rectilinear motion, undulating belly muscles to inch forward. But more typically, they throw a loop of the body forward, past its head, and then bring the rest of the body alongside it. This is the side-winding method they’re named for. It’s a good way to move through a sandy, hot environment … often with some speed. The tracks left behind are a series of unconnected lines with a “J” at the end, pointing in the direction of travel. This is different than is often expected by homeowners, who report a “sidewinder tracks” that are typically from fast-moving nonvenomous snakes, like coachwhips and whipsnakes, moving quickly through soft matrix, leaving a swishing side to side track.
And yes, there are sidewinders elsewhere in the world … but they’re not closely related to these snakes, and are not rattlesnakes. They are a great example of convergent evolution, where a similar solution evolves to meet similar problems. In this case, it turns out that side-winding is a very efficient way to move for a snake, and sandy deserts on the other side of the world are no different.
Webber, M. M., Jezkova, T., Glaudas, X., & Rodríguez-Robles, J. A. (2016). Feeding ecology of sidewinder rattlesnakes, Crotalus cerastes (Viperidae). Herpetologica, 72(4), 324–330. https://doi.org/10.1655/Herpetologica-D-15-00042
Tingle, J. L., & Sherman, B. M. (2022). Scaling and relations of morphology with locomotor kinematics in the sidewinder rattlesnake Crotalus cerastes. Journal of Experimental Biology, 225(7), jeb243817. https://doi.org/10.1242/jeb.243817
Blomsten, P., Schuett, G. W., Höggren, M., & Clark, R. W. (2016). Fifteen consecutive years of successful reproduction in a captive female sidewinder (Crotalus cerastes). Herpetological Review, 47(2), 231–234. https://www.academia.edu/download/43375448/Blomsten_et_al_Sidewinder_Reproduction_HR_2016.pdf
Rautsaw, R. M., Hofmann, E. P., et al. (2019). Intraspecific sequence and gene expression variation contribute little to venom diversity in sidewinder rattlesnakes (Crotalus cerastes). Proceedings of the Royal Society B: Biological Sciences, 286(1902), 20190810. https://doi.org/10.1098/rspb.2019.0810
Webber, M. M., Glaudas, X., & Rodríguez-Robles, J. A. (2012). Do sidewinder rattlesnakes (Crotalus cerastes, Viperidae) cease feeding during the breeding season? Copeia, 2012(1), 100–105. https://doi.org/10.1643/CE-11-056
Leavitt, D. J., & Grimsley, A. A. (2019). Density, recapture probability, biomass, productivity, and population structure of sidewinders (Crotalus cerastes) in the Sonoran Desert of Arizona. Herpetology Notes, 12, 577–584. https://www.biotaxa.org/hn/article/view/35147/44449
A Southwestern Speckled Rattlesnake resting along the top of a drainage after a night out. During the summer months, these and other rattlesnake species are primarily nocturnal, being encountered by people mostly in the hour before and after sunrise. As soon as the sun reaches the area, these snakes make a beeline for their aestivation sites to hide for the day.
The fact that rattlesnakes are often nocturnal and that they spend much of their lives avoiding excess heat is a surprise to many people. The misconception is that reptiles, ectotherms who get heat from the environment rather than produce it themselves, want it hot … the hotter the better. You’ll see this soon, in the form of comments like “it’s getting hot! It brings the rattlers out”, warnings from fire departments, and even articles in local news when temperatures stabilize in the triple digits for the year.
But thermoregulation means being the right temperature, not just as hot as possible. In fact, a body temperature sustained above around 105˚F can kill a rattlesnake. Interestingly, the upper terminal temperature seems to be similar across rattlesnake species, regardless of the environment they’re found. It’s often over 100˚F when these snakes begin their move back to their underground hiding spots, meaning they ride the line of death very closely, staying out as long as possible for the chance to find prey. If they are disturbed during this crawl for too long, or escape into the wrong hiding spot, it can quickly kill them.
We have learned this first-hand, unfortunately, from finding snakes within our study area who were first found by snake enthusiasts, likely mid-crawl. Thanks to Instagram, individual snakes that had died this way can be tied to individual events where a prolonged photo session and subsequent release of a heat-stressed snake resulted in death. To some herpers, it may seem like gatekeeping to discuss this kind of thing, but dead snakes are a lesson to those who would hear it.
During the summer, you may see us be critical of snake relocations performed by the fire department, and well-meaning individuals. This comes from the practice of releasing these snakes to improper cover, where they will be very unlikely to find survivable conditions in time. Every time you see a video of someone releasing a snake to open ground or random creosote mid-day, the relocator watches it crawl away and may be satisfied that they helped the animal … but these snakes do not survive for long.
Claunch, N. M., Lind, C. M., Lutterschmidt, D. I. (2023). Stress ecology in snakes. In Penning, D. A. (Ed.), The Stress Ecology of Reptiles. ResearchGate.
Cadena, V., Andrade, D. V., Bovo, R. P., Tattersall, G. J. (2013). Evaporative respiratory cooling augments pit organ thermal detection in rattlesnakes. Journal of Comparative Physiology A, 199(9), 883–893.
Castro, S. A., Prado, J. V., Wang, T. (2024). The relevance of vascular adjustments to hemodynamic control in the face of temperature change in Crotalus durissus. Journal of Experimental Biology, 227(15).
Laursen, W. J., Anderson, E. O., Hoffstaetter, L. J., Bagriantsev, S. N., & Gracheva, E. O. (2015). Species-specific temperature sensitivity of TRPA1. Temperature, 2(1), 142–157.
Kamees, L. K. (2022). Competing Behaviors of Thermoregulation and Ambush Foraging in the Timber Rattlesnake (Crotalus horridus horridus): A Mechanistic Assessment of Thermal Behavior (Doctoral dissertation, University of Arkansas).
Tattersall, G. J., Sinclair, B. J., Withers, P. C., Fields, P. A., Seebacher, F., Cooper, C. E., & Maloney, S. K. (2012). Coping with thermal challenges: physiological adaptations to environmental temperatures. In Comprehensive Physiology, Wiley.
LaDuc, T. J., Borrell, B. J., & Dudley, R. (2005). Respiratory cooling in rattlesnakes. Comparative Biochemistry and Physiology Part A, 141(4), 509–516.
Carnes-Mason, M. D., & Beaupre, S. J. (2025). Temperature manipulation induces ecdysis in lab-held rattlesnakes. Ichthyology & Herpetology, 113(2), 274–281.